ROTAX 447 Queries.

What should the tickover on a 447 be?  I was under the impression that it should be around 1800-2000rpm ?

I am being told that an engine in one of our ultralights is registering 800rpm tickover !!!!!!! ( I very much doubt it is )   I am also being told it is giving 3100rpm on max power ?   I am wondering whether an rpm gauge can under-read by 50% in any circumstances?

I have my suspicions on why it is being reported as those figures but I am curious to see what replies come from this site.